Alkylation of paraffins in presence of hydrofluoric acid



Patented Nov. 30,` 1948 ALKYLA'IION OF PARAFFINS IN PRESENCE FHYDROFLUGRC ACID 4Frederick E. Frey, Bartlesville, "0kla., `:assignerzto Phillips Petroleum Company, a .corporation lof Delaware ApplicationDecember '23, 1941, VSerial No. 424,204 13 claims. (o1. 26e-683.4)

'This invention relates to the catalytic production of higher boilinghydrocarbons from lower boiling hydrocarbons and more particularly tothe catalytic alkylation of paraffin hydrocarbons 'in the presence ofhydrofluoric acid. This application isa continuation-in-part of mycopending application, Serial No. 315,063, flied January 22, 194g, nowU. S. Patent 2,322,800, dated June 29, 194

In the presence of suitable catalysts, alkylatable hydrocarbons reactwith unsaturated hydrocarbons 'or other suitable allrylating reactantsto produce higher boiling hydrocarbons. The reaction, which `is known asalkylation, is promoted especially well by hydroluoric acid. Thiscatalyst yields excellent results with isoparains or other branchedchain parains and particularly paraiflns with at vleast one tertiarycarbon atom per molecule and with olens having more than two carbonatoms per molecule. However, under especially 'favorable circumstancesother parallins and/or oleins may react. Besides parailns, Aotheralkylatable hydrocarbons, such `as aromatic hydrocarbons, can be reactedwithV an Aallszylating reactant in the `presence of rhydrofluoric acidto produce higher boiling hydrocarbons. Suitable alkylatingreactants'forthe alkylation of either paraffins oraromatics include olelns,relatively polar nonprimary alkyl compounds, 'suchas 'tertiary andsecondary alkyl halides, advantageously fluorides kand chlorides,alcohols, and the like. The hydrouoric acid preferably should be aboveabout 80 per cent in strength and will generally be used with astrengthfgreater than 95'per cent; it is most advantageous when itissubstantially anhydrous, or 100 per cent in strength.

Because of its nonoxidizing character, hydrofluoric acid does notproduce the oxidationbw products'that are `formed in alkylation withsuch catalysts as sulfuric acid. Furthermore, Vhydrofluoric acid isrelatively `free from the tendency to form complex tarry additionproducts that'are formed `in alkylation with certainother catalysts.'However,v hydroluoric acid `is appreciably Vsoluble in saturatedhydrocarbons and its `use as a catalyst presents a yproblem of recoverythat is no, involved when other catalysts are used. y

In accordance with the present invention, the recovery of lhydrofluoricacid from mixtures containing hydrocarbons is facilitated by `fractionaldistillation, from at least `one solution originating in the alkylationprocess, and comprising hydroluoric acid and at least one-parain, ol alow-- boiling mixture comprising hydroiluoric lacid and a paraffinhydrocarbon.

.One object ofthls invention is torecover hydroiluoric :acid from amixture of hydrocarbons.

Another object of @this invention is to remove hydrciiu-oric .acid fromthe eflluent ol a `zone whereinalkylatable,hydrocarbons are alkylated inthe ,presence of hydrouoric acid as Ian .alkylat-ion catalyst.

.Another-object of this-invention is to produce a hydrocarbon fractionin the motor iuel boiling rangeibyithe alikylation of alkylatable.hydrocarbons in the presence of :hydrofluoric acid, such hydrocarbonfraction being substantially free from `hydroluoric acid.

`@ther objects and .advantages will be apparent from ythe accompanyingdisclosure and description. y

Adescription of ,the invention will be `famlitated by .a `.discussion.of v.the :accompanying drawing which shows Vsin kschematic form aniarrangernent of apparatus that `*is-especially well suited .for thealkylation :of a .low-,boiling isoparailin, such as isobutane or.isopentane For sake oi convenience the v drawing will `be described in:connection with ra process forthealkylation of an isoparailinhydrocarbon .although itis ywell within lthe scope of invention Etoemploy in Vmy proc-ess any alkylatable vhydrocar-ben and yparticularly.any a1- kylatable paraflin hydrocarbon.

v Whennalow-Lboiling.isoparallinicmaterial, preierably a material.containing substantial `quantities oressentla'lly. entirely lisobutane,enters @the system by .one or vmore inlets, such as inlet il havingvcontrol lvalve t2, it is preferably accompanied -by 1a Arelativelyminor .proportion-of 4the alkylating react-ant, such-.as .one `or moreoleil-ns, but it may enter the ksystem in the substantial absence of lanalkylating .-reactant, provided that the alkylating .reactant `enters byone or more other inlets, not shown inthe drawing. The isoparainicmaterial andthe alkylating reactant pass into -alkylato-r :i3 whereinthey are intimately contacted with liquid concentrated hydrouoric acidwhich enters :the alkylator through 'inlet LM having control valve l5.Under Athe influence of .the'hydrofluoric acid, an isoparailinhydrocarbon and .an alkylating reactant .react to produce ahigher-bolingparain.

The .alkylation conditions in kalkylator .i3 may bei varied widely butthey are preferably so selected as Y.tn favor alkylation and tovmirri-mine n side .reactions such .as "reactions producing4.relatlvelyflheavy unsaturated vhydrocarbons vand/or ilumine-containingcompounds. To .this .end the instantaneous concentration. of 'alkylatingrelarly pure hydrocarbons, orra motor fuel stock 1 of particularly highoctane number, aredesired, the mole ratio of isoparain to alkylatingreactant may need to be as high as 50:1 or 100:1' or even greater forany particular point at which alkylating reactant is introduced,V.but-generally satisfactory conditions will be found when the moleratio of isoparafiinv to alkylating reactant is between 12:1 and 100:1.Accordingly, multipoint addition of the alkylating reactant to thereaction zone is advantageous, asin Frey 2,002,394.

The ratio of hydrofluoric acid to hydrocarbons 24 the hydroiiuoric phaseis fractionally distilled into the following fractions: a major fractioncomprising chiefly anhydrous hydrouoric acid and including theisoparaffin present in solution l in the acid phase, that is passedthrough conduit having valve 2G into acid-recycle conduit 2l,

by Whichit is recycled to alkylator I3; and a should be high enough sothat a'large acid surface may be readily maintained; a ratio ybetweenabout 1:1 and 1:10 by volume is generally satisfactory, ibut at timesthis range may be exceeded in either direction. Thel temperaturepreferably may be that obtained by such simple cooling means as awater-cooled heat-exchange coil, but no special refrigeration is needed.A temperature in the range of 'Toto 130 F. is'preferred, however, verygood results are obtained at temperatures of the order of 150| F.1ormore whereupon conta-ct time can be appropriately decreased.

The average time of contact of the reactants with the acid may vary froma minute or less to an hour or more; in general, such alkylationreactions conducted .at-lower temperatures of operation require Ilongercontact time than those conducted atthe higher temperatures. A time ofcontact of 5to l0 minutes is preferred at 'ordinary temperatures. Ahighfp-ressuremay be used but it need not greatlyexceedthat required tomaintain the reactants `in the liquid phase; if. desired an increasedApressure may be maintained by pumping molecular hydrogen into thereaction mixture, `whereby'the catalyst life of the hydrouoric acid maybe advantageously prof. longed. Intimate contacting'of the reactants andacid isdesirable and lmay be effected by mechanical agitation orpreferably by turbulence generated by injection ofthe reactants into theacid at-highbvelocity, as byl ejection from one or more'jets at whichthere is a high pressure drop, preferably in excess of about 50 rpoundsper square inch, whereby an emulsion of the hydrocarbon and the acidphasesis formed.

After a suitable reaction,1period,--or time-of contact, the reactionmixture is passed from alkylator I3 through conduit I6 having valve `I'Iinto separator I8, in whichit is separated, as by gravity, into ahydrocarbon phase and a relatively denseacid phase. During theseparation, ele-l vated temperature preferably should be avoided,

since the mutual solubility of ,liquid hydrocarbons and liquidhydrouoricy acidi increases with in criease in temperature; forexamplenin therange of 32 to 140 F., the solubility of hydrouoric acidin isobutane increases linearly' from 0;3 to 0.9 per cent by weight, andthe solubility of isobutane in hydroiluo'ric acid increases` from 1.8 to4.0 per cent. v1For improved separation of the two phases, the.temperature may( be' advantae geously lowered somewhat' below theAordinary temperature, preferably toa temperature in the range of -40 to502111.,v or `even lower.y V.The acid minor fraction, comprising an oilof organic compounds and a maximum-boiling mixture of hydrofluoric acidwith any Water introduced into the system with the reactants orotherwise, that is withdrawn as a residue through outlet 2l having valve26. The maximum-boiling mixture advantageously may be separated from theoil and maybe treated to recover its content of hydronuoric acid, whichmay then be reused in the process. Thus, the combined oil-acid-watermix-A ture passing through conduit 27 may bepassed therefrom throughconduit 'i5 to separator 16, wherein the oil is separated from theaqueous hydrofluoric acid. The oil is discharged through conduit 'Ilandthe aqueous hydrouoric acid is passed through conduit 'I8 todehydration means i9 for treatment to effect separation of water andhydrogen fluoride. The treatment may comprise conversion of the waterinto hydrogen and oxygen by electrolysis, or kit may comprisedistillation, either alternately at different pressures or after theaddition of a strong relatively nonvolatile dehydrating agent such assulfuric acid or the anhydride of sulfuric or phosphoric acid. Such a.distillation with sulfuric acid is more thoroughly disclosed in myapplication Serial No. 647,588, filed February 14, 1946. Water soremoved is discharged from dehydration means 'I9 through conduit Bilandsubstantially anhydrous, purified vhydroiiuorc acid is passed throughconduit 8l to acid recycle line 2I. y

In some instances it may be desirable to separatethe organic oil in afirst fractionation and the aqueous 4Ir'aximum-boiling aqueous mixturein asecond fractionation. Thus, fractionator 24 may be operated so thatonly an oil is passed through conduit 21, and a low-boiling fractioncomprising hydrofiuoric'acid and isoparafn, as discussed above,`together with some water is passed throughthe rst part of conduit 25,and is passed therefrom through conduit 85 to fractionator B. Ahigh-boiling aqueous hydrofluoric acidis removed from fractionator 86through conduit 81, and an anhydrous hydrofluoric acid fraction,together with some isoparaiin, is removed from fractionator 86 throughconduit 88, and may be returned Vto thesystemthrough conduit 88 toasubsequent part of conduit 25.

It will often be desirable, however, to remove from the process at leasta portion of the major fraction comprising hydroiluoric acid andisoparaiin present in solution through conduit 68 controlled by valve69. Such a fraction may be y treated in means not shown to recover itscontent of hydrouoric acid which may then be reused in the process byintroduction through/conduit I4.

monaca The hydrocarbon phase separated from the alkylation mixture inseparator I8 is forced, as by pump 29, through conduit having valve 3|into fractionator 32. In this iractionator, it is fraetionally distilledinto the following fractions: a low-boiling fraction, comprising theexcess of unalkylated isoparafin and the hydroiiuoric acid dissolved inthe hydrocarbon phase, which is .subsequently passed through conduit 33having valve 34 and then back to alkylator I3, as through acidrecycleconduit 2| an isoparain fraction that is recycled to alkylator I3, asthrough conduit 35 having valve 36; and an alkylate fraction, comprisingthe higher-boiling parafns resulting from the alkylation, that iswithdrawn through outlet 3l having valve 38 to storage or to additionalprocessing steps, not shown.

In addition, one or more otherfractions may be produced in fractionator32, depending upon the exact composition of the hydrocarbon materialentering this fractionator. If this material contains a relativelyunreactive parafn of the same molecular weight as that of theisoparaffin, an unreacted paraffin fraction is advantageously withdrawnthrough outlet 39 having valve 4|.'I, and it may be processed, as bycatalytic dehydrogenation or cracking, to provide olens to be used inthe alkylation step; for example, in the alkylation ci an isoparaiiinwith one or more butylenes, any part or even substantially all of anynormal butane introduced with the reactants and/or formed during thealkylation may be so Withdrawn. Also, if the hydrocarbon materialentering fractionator 32 contains a relatively lowboiling paraffinhaving a boiling point substantially below that of the isoparaihn, alow-boiling fraction, comprising at least part of the lowboiling paranand at least part of the dissolved hydroiiuoric acid, is distilledbefore the fraction comprising the isoparain; for example, in thealkylation of an isoparafln with propylene or a. polar isopropylcompound, such as the alcohol, the uoride, the chloride, or the like,any part or even substantially all of any propane introduced with thereactants and/or formed during the alkylation may be so distilled. Thisfraction may be withdrawn from the system through outlet 4I having valve42, but at least part of it is preferably passed through conduit 43having valve 44 to separator 45. In this separator, the fraction isseparated, as by cooling and/or settling, preferably at a temperaturebelow 50 F., into a hydrocarbon. phase and an acid phase. The acid phasemay be recycled, as by pump 48, through conduit 41 having valve 48 andthrough acid-recycle conduit 2|, back to alkylator I3; however, at leastpart of it may be passed through conduit 49 having valve 50 intofractionator 5I. In this fractionator, the acid phase is fractionallydistilled into the following fractions: a lowboiling fraction,comprising part of the hydrofluoric acid and substantially all of thelight parafn dissolved in the acid phase, that is recycled throughconduit 52 having valve 53 and through conduit 43 to separator 45; and aresidual fraction, comprising chiefly hydrofluoric acid, that isrecycled through conduit 54 having valve 55 and through acid-recycleconduit 2l to alkylator I3. The hydrocarbon phase separated in separatormay be withdrawn from the system, advantageously if the separationtemperature was sufficiently low for the solubility of hydrofluoric acidto be negligible, through outlet 56 having valve 5l; but usually atleast part of it is preferably returned at a suitable temperaturethrough 6.). conduit 10-and= valve 1I toiracti'onator, or `frac--tionating means, v32.as .a reflux stream. All of the stream Amay be so..returned when the amount of low-boiling hydrocarbon material is small,and inert material maybe discharged from the system as through conduit39. When additional fractionation is desired, a. part or all of thestream may be passed from conduit 5B to subsequent fractionation. steps,as by pump 53, through conduit 59 vhaving val-ve 60 into fractionator5I. In this; fractionator, the hydrocarbon phase is fractionallydistilled into the following fractions: a low-boiling fraction,comprising part of the light parain and substantially al1 of thehydroiiuoric acid `dissolved in the hydrocarbon phase, that is recycledthroughv conduit B2 having valve 63 and through conduits 52 and 43 -toseparator 45; and a residual fraction, comprising substantially acidfreelight paraiin, that is withdrawn from the system throughoutlet-64 havingvalve 65.

When .an aromatic hydrocarbon is alkylated with an alkylating reactantin the. presence of hydroiiuoric acid .and when, for example, it isdesired to remove hydrofluoric acid iro-m the hyv drocarbon productaccording to my invention, it

is usually necessary for an inert low-boiling hydrocarbon to be presentin the charge to the alkylation zone and/or by being added to thematerial passed to fractionator 32. Under such circumstances conditionsin fractionator 32 are so controlled that a low-boiling fractioncomprising an added inert low-boiling hydrocarbon and substantially allof `the hydrofluoric acid which had been vpassed tothe iractionator 32through f conduit 30 is distilled from the product and passed `throughconduit 33v back to alkylator i3, When a low-boiling olefin is thealkylating reactant ffor a-n aromatic hydrocarbon 'there will usuallybe. an inert low-boiling hydrocarbon present. iin the charge 'to thealkylator I3 and a suflicientY amount of it will be passed tofractionator '32 vso that inert low-boiling .hydrocarbon `material :froman outside source will not need to beA added tothe material passedthrough conduit 30. An excessive amount of inert hydrocarbon materialcan be` prevented vfrom. overloading the system by being vented throughconduit 4I either as such or associated with acid catalyst. When lsuchan inert hydrocarbon is associated with acid catalyst it is separatedtherefrom in a manner as discussed herein.

l By fractionator, as used in this specification, is meant any system offractional distillation devices that will effect the results indicated;it may consist of one or more than one fractionating column, as is foundto be necessary or desirable in accordance with the well-knownprinciples of 'fractional distillation. Many other well-known devicesnot specically shown or described in this specification, which are knownto improve the attainment of the results indicated herein, may beincorporated or used without passing beyond the scope of this invention.

"The following examples specically illustrate, among other things, theaspect ofthe invention relating toire'covery of hydroiiuoric aciddissolved in the hydrocarbon phase, without necessarily limiting the-invention.

To 8.38 lbs. of anhydrous hydroiiuoric acid in an Iii-literk steel bombprovided with a 540- R. P. M. stlrrer was added 15.87 lbs. of isobutane.During4 15 minuteswhile,the-.mixture was stirred,

1.67 lbs. ofanisobutylene concentrate containing 76:22 per. centbyweight of isobutylene and 23.78 percent isobutane, was added. Theresulting mixture was stirred for 6 Vminutes more; the average contacttime Was 13.5 minutes. The temperature during the stirring was 100 to106 F.; the pressure was 94 to 101 lbs. per sq. in. gauge. The over-allmol ratio of isobutane to olens was 12.34;*-the over-all volume ratioofl hydrocarbons to acid was 3.77. At the end of the stirring, the twoliquid phases were allowedl to'separate; 8.32 lbsj of the lower or acidphase was withdrawn into a storage cylinder; and 5.81 lbs. of theremaining material, which still-contained a small portion of the acidphase, was charged into a 6.2-liter kettle attached to `an 8-ft. steelfractionating column packet with 121-111. Raschig rings of fcarbon.Subsequently, after distillation of this rst batch of material chargedto the kettle, two additional batches,`of 5.55 and 5.92 lbs., werecharged to the kettle, each being added to the residue from thepreceding batch. Table I gives data obtained during the rst part of thedstillation of the rst batch to effect debutanization of the alkylateand recovery of dissolved hydrouoric acid.

TABLE I amounted' to 1670 cc.; this volume represented a yield of 202.3per cent by Weight of the olen used in the alkylation, or 99.3 per centby weight of the theoretical alkylation yield of iso-octane. The productwas completely saturated; it contained only 0.0024 per cent by weight oforganically combined yiluorine. Only 5.8 per cent of it by volume boiledbelow the octane range, and only 3.3 per cent boiled above this range;90.9 per cent boiled in the octane range. The fraction boiling to3695-13. amounted to 99.1 per cent by volume of the total alkylate. Thisfraction had a Reid vapor pressure of 3.10 lbs. and a gravity of 69.8 A.P. I. tsAjS. T. M. octane number was as follows: 0 cc. TEL, 95.5; l cc.TEL, 102.9; 3 cc. TEL, 107.8. Its A. S. T. M. distillationcharacteristics were as follows: rst drop, 160 F; 10 per cent, 205 F.;per cent, 216 F.; 90 per cent, 228 F.; end point, 337 F.

EXAMPLE II In the course of a thoroughgoing basic investigation'ofhydrouoric acid alkylation of paraiiins, there was obtained a mixture ofhydroiluoric acid and light parains, principally propane. This mixturewas fractionally distilled in the column Azeotropz'c distillation ofsobutane and hydro-y fluoric acid;

Volume cc. Distilled Wt. per Distillation Conditions 78o Q cent of wpa]Fraction Temp' o F Pressure Redux 1b' [SCL mi ratio Mixt. HF IsobutaneHF Head Kettle i 88 129 82 5. 6 100. D 22. 0 2. `2 61. 8 86 118 73. 5 9.1 100. 0 l1. 0 4. 7 92. 7 93 110 57 l0. 4 100.0 2. 5 7. 4 99. 6 7. 1100.0 0.05 10. 2 99.8 50.0 trace 11.7 99.9 90 128 82 7.1 100. 0 0. 0514. 4l 100.0 91 108 54 100.0 0.00 17. 6

These data show that the hydrofluoric acid was distilled together withisobutane as a lowdescribed in Example I; Table II gives a summary ofthe data obtained.

TABLE II Azeotrop'z'c distillation of propane and hydrofiuoz'c acidVolume cc. Distilled Wt. A Dxstillation Conditions 780 C.) per cent oftotal Fraction Tempuoy lllf-/essflif lx. Mm. Br camere. Hr Head Kettle63 s4 160 5.6 74 0.0 2.3 0.0 73 89 105 as 75 0.1 4.5 0.8 `75 s0 157 3.4220 9.5 10.9 12.4 75 a9 101 10.8 230 20.4 17.3 39.0 77 91 174 14,4 28728.0 25.1 75.3 es 97 109 4.9 520 7.5 40.9 84.5 75 9a 104 0.1 583 10.961.5 00.9

These data show that at rst, when parains boiling mixture. By the timethe rst tenth of the total isobutane had been distilled, practically allof the hydrouoric acid had been removed from the kettle, even thoughsomeof the hydrouoric acid phase was present in the charge and even thoughthe column was `a rather ineicient one, as a preliminary distillation ofa mixture of benzene and carbon tetrachloride had shown it to beequivalent at best to only about twelve theoretical plates.

Upon complete debutanization, the alkylate lighter than propane weregoing overhead, relatively little hydrofiuoric acid distilled with thelightparafns. Then, when what was substantiallyanazeotropic mixture ofpropane and hydroiiuoric acid was going overhead, the content of'hydroluoric acid in this azeotropic mixture Was-practically 10 per centby volume, measured atthe temperature of carbon dioxide snow, or 19percent by weight. After distillation of such an azeotropic mixture,thedistillate again contained 9 a relatively small 'concentration :off/hydrofluoric acid, apparently because of vsorption by :the-'carbonpacking in .the column, since analysis of the residue lin the kettleshowed that thev residue 4contained less than 0.005 per centhydrofluo-ric acid. In spite of the lexcessive amount ofy hydrofluoricacid, which was greater' than that :corresponding to the solubility of.the .acid in the hydrocarbon, as Was evidenced by the presence of some.acid phase in the mixture charged to the column, three fourths of theacid was distilled when .only one fourth of the hydrocarbon had beendistilled. The data thus demonstrate the excellent :concentration orrecovery of hydrofluoric vacid that can be effected by distillation as alow-boiling substantially azeotropic mixture with propane. Much betterconcentration would have been obtained with a column of relativelygreater efficiency, especially one Without such a porous packing ascarbon rings, which apparently tended to retain hydrofluoric acid,thereby yprolonging the period during which hydrofiuoric acid continuedlto be `present in the distillate.

The foregoing examples illustrate batch 4operation, but continuousoperation is preferably practiced in the production of relatively largequantities of alkylate, as will be readily appreciated.

Because the invention may be practiced otherwise than as specificallydescribed or illustrated, and because many modifications and variationswithin the spiritjand scope of it will be obvious to those skilled inthe art, the invention should not be unduly restricted by the foregoingspeciflcation and examples.

I claim:

l. In a process of alkylat-ing a 10W-boiling alkylatable paraffin inthev presence of hydroluoric acid, the steps which comprise separatingfrom an alkylation reaction mixture originating in such a process aliquid acid phase comprising hydrofluoric acid associated with.dissolved organic impurities formed during said alkylation, and adissolved low-boiling paraiiin, and Water introduced into the processwith said parafiin reactant, fractionally distilling from said acidphase a lowboiling mixture containing substantiallyl all of saiddissolved low-boiling paraiiin and a sufficient amount of saidhydroiiuoric acid to form la minimum boiling azeotropic mixturertherewith, treating the residue to remove Water and said dissolvedorganic impurities and to recover all of its content of hydrofluoricacid in such condition that it is suitable for reuse for eiectingalkylation, and passing puri-lied Asubstantially anhydrous hydrofluoricacid so obtained to said alkylation reaction.

2. The process of claim l in which said treating comprises electrolysisof said water.

3. The process for producing substantially saturated hydrocarbonssuitable for use in motor fuel, which comprises alkylating a low-boilingisoparafn hydrocarbon with an olefin in the presence of hydrofluoricacid, passing eiiluent from said alkylation reaction to a rst separatingmeans, removing from said first means a liquid acid phase containing aminor portion of dissolved organic impurities and low-boiling parafiinhydrocarbons and a major portion of hydrouoric acid, passing said liquidacid phase to a rst fractional distillation means, distilling therefroma low-boiling mixture containing substantially all of the dissolvedparain hydrocarbon and at least a sufficient amount of said hydrofluoricacid to form a minimum-boiling azeotropic mixture With said dissolvedparaffin, recovering from .said low-boiling :mixture its content ofAhydrofluoric acid and returningl at 'least a portion of said recoveredhydrofluoric acid freed from paraffin hydrocarbon to the alkylationzone, removing also from said first separating means a hydrocarbon phasecontaining a major portion of synthesized and unreacted hydrocarbons anda minor portion of dissolved hydroiiuoricA acid, passing suchhydrocarbon phase to a -second fractional distillation means anddistilling therefrom a low-boiling mixture containing substantially allof the dissolved hydroiiuoric acid and at least a portion of unreactedhydrocarbons .recovering hydrofluoric acid from said low-boiling mixtureand returning same to said alkylation Zone, distilling from hydrocarbonsfreed from hydrouoric acid by said second fractional distillationunreacted hydrocarbons and returning at least a portion thereof to thealkylation zone, and distilling therefrom also a fraction comprisingsynthesized hydrocarbons suitable for use in motor fuel.

4. The process for producing branched-chain saturated hydrocarbons byreacting a low-boiling isoparafn with olens, which comprises alkylatinga low-boiling isoparafin with an olein in the presence of a liquidhydrofluoric acid alkylation catalyst in an alkylation zone, separatingfrom an eiiluent of said alkylation Zone a liquid hydrocarbon phase anda used hydrofluoric acid catalyst phase associated Withdissolved organicimpurities formed during said alkylation and Water introduced into theprocess with said reactants, returning a portion of said used catalystto said reaction Zone, passing a further portion of said used catalysttoa first fractional distillation Zone and distilling an anhydrousfraction comprising hydrofluoric acid from said dissolved organicimpurities and Water, passing said liquid hydrocarbon phase to asecondfractional distillation :Zone and recovering dissolved hydrogenuoride Vtherefrom, kand returning hydrouoric acid from each of saiddistillation zones to said alkylation zone.

5. An alkylation process which comprises reacting a low-boilingisoparain hydrocarbon With an oleiin hydrocarbon in the presence ofA aconcentrated hydrofluoric acid alkylation catalyst under alkylationconditionsto produce higherboiling parafn hydrocarbons in an alkylationzone, passing eiluents of said alkylation zone to separating means underconditions such that liquid hydroluoric acid separates as a separatephasev from a' hydrocarbon phase, said liquid hydrofluoric acid yphasecontaining dissolved heavy organic impurities formed during saidalkylation and Water introduced with said reactants, passing a portionof saidfhydrouoric acid phase back to-said a'lkylation zone, subjectinga further portion of said hydrofluoric acid phase to fractionaldistillation to separate as a distillate a fraction comprisingsubstantially anhydrous hydrofluoric acid from 'a high-boiling fractioncomprising said dissolved heavy organic impurities and said Water,returning said distillate to Said alkylation Zone, subjecting saidhydrocarbon phase to a second fractional distillation to separate a10W-boiling fraction comprising essentially al1 hydrofluoric acidassociated with said hydrocarbon phase together with at least suilicientlow-boiling paraffin hydrocarbon material to form a minimum-boilingazeotropic mixture therewith, cooling and condensing said low-boilingfraction to form a hydrocarbon phase and a liquid hydrofluoric acidphase, and passing the last said liquid hydrofluoric acid phase to saidalkylation zone.

yeficaces l i V6. The process of claim 5 wherein said isoparafiincomprises isobutane.

7. An alklation process which comprises reacting an isoparaln with apropylene-containing fraction in the presence of a hydrogen fiuoridecatalyst, separating the bulk of the hydrogen fluoride catalyst from thehydrocarbon products,

` returning at least a portion of said separated hydrogen fluoridecatalyst to the alkylation step, introducing the hydrocarbon productscontaining a relatively small amount of dissolved hydrogen fluoride toa. first fractionation step and therein vaporizing a fraction comprisingpropane and hydrogen fluoride, condensing said propane-hydrogen uoridefraction to form a hydrogen uoride layer and a hydrocarbon layercontaining hydrogen fuoride, returning said hydrogen fiuo- 4 ride layerto the alkylation step, introducing said hydrocarbon layer to a secondfractionation step and therein vaporizing a sufiicient quantity ofpropane to separate substantially the total hydrogen fluoride content ofsaid hydrocarbon layer,

supplying the hydrogen uoride and propane vapors separated in saidsecond fractionation step to the aforesaid condensing step, andwithdrawing from said second fractionation step propane which issubstantially free from hydrogen fluoride.

8. The process of claim 7 wherein said isoparan comprises isobutane.

9. `An alkylation process which comprises reacting an isoparafiln with apropylene-containing fraction under alkylating conditions in thepresence of hydrogen fluoride, separating the bulk of theused catalystfrom the hydrocarbon reaction products, returning at least a portion ofsaid used catalyst to the alkylation step, subjecting another portion ofsaid used catalyst to treatment includingdistillation wherein hydrogenfluoride is separated from organic contaminants present vin said usedcatalyst, returning the hydrogen fluoride separated in said treatmentincluding distillationto said alkylation step, introducing saidhydrocarbon reaction products containing a relatively small amount ofdissolved hydrogen fluoride to a first fractionation step and thereinvaporizing' a fraction comprising propane and hydrogen fluoride fromhigher boiling hydrocarbons, condensing said fraction to form a hydrogenfluoride layer and a hydrocarbon layer containing `hydrogen fluoride,returning said hydrogen fluoride layer to the alkylation step,introducing vthe hydrocarbon layer to a second fractionation step andtherein vaporizing a suiflcient quantity of propane to separatesubstantially the total hydrogen fluoride content of said hydrocarbonlayer, supplying the hydrogen fluorideandV propane vapors separated insaid second fractionaton step to the aforesaid condensing step,recovering from said second fractionation step a propane streamsubstantially free from hydrogen fluoride, separating also in said firstfractionation step unconverted isoparaln from higher-boilinghydrocarbons, and returning said unconverted isoparaflin to thealkylation step.

10. The 4'process of claim 9 wherein said isoparain comprises isobutane.

11. The process of claim 9 wherein at least a portion of the hydrogenfluoride separated in said distillation is subjected to furtherfractionation wherein substantially anhydrous hydrogen fluoride isseparated from a hydrogen fluoride-water mixture and said substantiallyanhydrous hydrogen iiuoride is returned to the alkylation step.

12. The process of claim 7 wherein said alkylation step is conducted atan alkylation temperature not greater than about F. and under sufcientpressure to maintain the catalyst and hydrocarbons substantially in theliquid phase.

13. In the alkylation of an isoparain with an olenic fraction containingpropane in the presence of hydrogen fluoride catalyst wherein there isseparated from the bulk of the catalyst a hydrocarbon mixture containingpropane and dissolved hydrogen uoride, the method which comprisesfractionating said mixture to vaporize the propane and hydrogen fluoridetherefrom, condensing the resultant vapors thereby forming a hydrogenfiuoride layer and a propanelayer containing hydrogen fluoride,returning the firstmentioned layer to the alkylation step, subjectingthe second-mentioned layer to further fractionation and vaporizing asucient quantity of its propane content to carry off as vaporsubstantially all of the hydrogen fluoride contained in saidsecond-mentioned layer, commingling the resultant vapors of propane andhydrogen fluoride with the vapors from the first-mentioned fractionatingstep for condensation therewith, and removing from the second-mentionedfractionating step a propane fraction substantially free of hydrogenfluoride.

FREDERICK E. FREY.

REFERENCES errar) The following references are of record in the die ofthis patent:

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